What are those Clusters Anyway?

Black Welsh Mountain sheep in North America are highly inbred. Our founding population was very small so we do not have much variation from which to select. In the USDA’s National Animal Germplasm Program performed a cluster analysis study on the population. This study looks at the population as a whole and the full pedigree information and calculates how closely related every sheep is to every other sheep. Then those animals are sorted and groups can be made of aniamls that are more closely related compared to the rest of the population.

Studies like this have shown that for some breeds where there are numerous individuals there is actually very little genetic variation between them such as modern Holstein cattle. The population is huge but there are very few different strains or bloodlines within that population so the overall genetic diversity is low.

Within the Black Welsh Mountain breed this study showed that there were 8 main clusters or bloodlines of sheep within the breed. Of these Cluster 7 existed in Canada only. Cluster 2 existed in a single flock on the east coast. Cluster 5 existed in a single flock on the west coast and Cluster 3 existed in only 2 flocks on the west coast.

Within the breed reading the cluster analysis tree from left to right the clusters are related to each other in this order:

8, 6, 7, 3, 5, 4, 2, 1

So 1 and 2 are more closely related than 1 and 8 and so on. The 3 largest clusters in terms of numbers of animals in the national flock are 4, 6 and 8.

Here at Desert Weyr we have been maintaining separate breeding groups of sheep in Clusters 4, 6 and 8. We have also used rams in clusters 2, 3 and 1 as line cross mates for our ewes.

We have noticed some differences between the clusters.These are general and individual animals can be different.
Cluster 4 is the most prolific. In our flock the ewes that produce and raise triplets are typically in cluster 4 or a cross of cluster 4 and 6. Most of these ewes will twin with a few singles and some triplets. Typical live lambs per ewe bred for this group is 165% or more. This group also tends to have softer wool than the others. Their high production mean these sheep need high quality forages although they still should not need grain. Poor quality grasses will not allow them to express their full potential and their softer wool is not quite as good for extreme harsh environments unless they have some shelter.

Cluster 6 is the general purpose sheep. Their wool type ranges from coarser to finer and they are moderately meaty. They are not extreme in any given characteristic. A few of these ewes will produce triplets but most will twin with some singles. Typical live lambs per ewe bred for this group is 140-150% These are good solid sheep with the ability to perform in almost any environment.

Cluster 8 are wooly tanks. They are the heaviest and meatiest of our sheep. They are also the “hard men” with the longer coarser outer coat of wool and thick manes. Their wool is nearly always very coarse and they have the heaviest thick horns of all the clusters we have raised. Many of these ewes are twinners with the rest singles. Typical live lambs per ewe bred for this group is 140%. This cluster can produce a nice single or twin lamb on rough forages and will survive the harshest winters with little to no shelter.

This fall with out continuing drought we have decided to reduce our breeding flock by 1/3. Since we still wish to maintain separate clusters and continue our breeding program we have elected to offer for sale all of Cluster 4. These sheep are the most prolific and are more likely than other clusters to produce triplets. This is not an advantage when our forages are poorer quality and the ewes get so far milked down it’s hard on them to regain enough condition for the next set of lambs. This cluster will do better in a slightly softer environment with lusher more nutritious forages that can support their additional lambs. Our altitude, harsh winter climate and poorer forages make Clusters 8 and to a lesser extent 6 the best sheep for our farm.

Thus all of our remaining Cluster 4 and 4 Cross sheep and a selection of sheep from our other clusters are now offered for sale.

Check out the sales list for what is available. We will be adding lambs over the next few weeks as we finish evaluations.